nities, and behavior of the family. In particular, an attempt is made here to trace the effects of population growth and economic development on the allocation of family resources. The most difficult problem for such an analysis is to separate cause and effect; the family's changing environment and behavior both cause the acceleration of population growth and simultaneously generate new environmental constraints that presumably exert an influence on family behavior. Formal analysis of these problems within an econometric framework (2, 3, 4) has recently begun, but much more work is needed to make a firm identification of the important interactions between economic and demographic variables in the development process. The approach of this paper is, first, to develop a simple model of family behavior in which reproductive behavior is central; second, to identify how economic development and the acceleration in population growth affect the family's environment; and third, to infer from this framework what consequences, both transitory and permanent, are likely to follow from mounting population pressures. All the references in this paper pertain to rapidly growing, low income populations unless otherwise stated. THE VALUE OF CHILDREN: A MODEL Children certainly are not merely the unintended outcome of sexual activity. On the contrary, children are a source of satisfactions to their parents and the value of these satisfactions depends on an array of psychological, social, and economic needs. I shall assume in this inquiry that reproductive behavior (fertility) is largely a response to the underlying preferences of parents for children, preferences which are constrained by uncertain fecundity and unreliable birth control. Given this working hypothesis, how might these preferences be revealed in micro data? The first task is to search for ways to identify the determinants of demand for children by looking for different aspects of the human environment that are likely to change the demand for children. The most intractable problem is that of distinguishing between the demand for children and their supply, because parents are both the demanders and suppliers simultaneously (5). If at first one neglects the sources of uncertainty on the supply side of the problem, the desired reproductive behavior of parents is seen to depend on the following underlying values. With respect to the demand there are first, the satisfactions of having a child (psychic utility that appears intangible because of the nonpecuniary context in which these satisfactions are obtained); and second, the tangible returns that accrue to parents because of their child's future contribution to the parents' real income. With respect to the supply there are first, the opportunity costs* and psychic cost of the parents' time and effort in bearing and *Potential loss from not usinc one's time and cnercv in alternative activities.hould not be taken very seriously. Thus the extraordinarily high correlation of telephones (i.e., a surrogate for modern infrastructure) with natality is reduced from -0.94 to -0.88 when Argentina and Uruguay arc excluded.